Presently, wear resistance, sliding properties, and fracture resistance of cutting tools, wear-resistant members, and sliding members that are required to exhibit wear resistance, sliding properties, and fracture resistance are enhanced by using a technique of forming a coating layer on surfaces of a substrate composed of a sintered alloy such as a cemented carbide or cermet, a sintered high-hardness compact such as diamond or cubic boron nitride (cBN), or a ceramic such as alumina or silicon nitride.
Extensive studies have been conducted on methods for forming the coating layer in which a physical vapor deposition technique such as an arc ion plating technique or a sputtering technique is used to form a nitride layer containing Ti or Al as a main component, and continuous improvements have been made to extend tool life. Various innovations in addition to those related to the elements used in the coating materials have been applied to these surface-coated tools having coating layers in order to comply with changes in cutting environment such as increasing cutting speeds and diversification of workpieces.
For example, PTL 1 describes a surface-coated tool in which surfaces of a substrate are coated with a coating film such as TiAlN and that progress of welding and wear at a rake face can be suppressed and notch notch wear at a flank face can be suppressed by adjusting the Ti ratio in the flank face to be higher than the Ti ratio in the rake face.
PTL 2 describes formation of a TiAlN-based hard coating film having a thickness of 1 to 5 μm on surfaces of a substrate and that the hard coating film exhibits improved welding resistance and wear resistance since the area fraction of coarse particles that are larger than the film thickness and are present in the hard coating film is adjusted to be 5 area % or less, and the surface roughness Ra of the hard coating film is adjusted to 0.1 μm or less or the surface roughness Rz is adjusted to 1 μm or less.